Nature of ore-fluids of intracontinental intrusion-related hypothermal deposits and its difference from those in island arcs.

This paper summarizes 60 intrusion-related hypothermal deposits in China, including usually named porphyry, skarn, breccia pipe, vein and IOCG types. These deposits were formed and located in continental orogenic belts, fault-controlled magmatic belts and reactived intracontinental orogens or cratonic margins. All of these deposits display intense H_2O-poor wallrock alteration, such as K-feldspathization, epidotization, fluoritization and carbonation, and weak H_2O-rich alterations, such as sericitization, chloritization and biotitization. Fluid inclusion data indicate that the ore-fluids forming intracontinental intrusion-related hypothermal deposits are characterized by CO_2-rich and high salinity, together with high contents of F and K, contrasting to the CO_2-poor NaCl-H_2O fluids commonly observed in volcanic arcs. It is concluded that the differences in ore-fluid and wallrock alteration result from contrasting compositional sources, i. e. the ratios of K/Na, F/Cl and CO_2/H_2O are high in continental crust, whereas, low in oceanic crust.